#include <bits/stdc++.h>
using namespace std;

int main() {
    int n, m, index = 0;
    bool fx = false;//false->Left to Right   true->Right to Left
    string s;
    cin >> m >> s;
    n = ceil(s.size() * 1.0 / m);
    char arr[n + 5][m + 5];
    for (int i = 1; i <= n; ++i) {
        if (!fx)
            for (int j = 1; j <= m; ++j)
                arr[i][j] = s[index++];
        else
            for (int j = m; j >= 1; --j)
                arr[i][j] = s[index++];
        fx = !fx;
    }
    for (int j = 1; j <= m; ++j)
        for (int i = 1; i <= n; ++i)
            cout << arr[i][j];
    return 0;
}